U.S. patent number 5,178,943 [Application Number 07/489,082] was granted by the patent office on 1993-01-12 for biaxially oriented polyester film.
This patent grant is currently assigned to Teijin Limited. Invention is credited to Takeo Asai, Tadashi Ono.
United States Patent |
5,178,943 |
Asai , et al. |
January 12, 1993 |
Biaxially oriented polyester film
Abstract
A biaxially oriented polyester film composed of an intimate
mixture of an aromatic polyester, barium sulfate particles having
an average particle diameter of 0.1 to 10 micrometers, and an
alkali metal or alkaline earth metal salt of a higher fatty acid
having 8 to 34 carbon atoms. The fatty acid metal salt has a
melting point in the range of 120.degree. to 320.degree. C. The
biaxially oriented polyester film has substantially no difference
in surface properties such as roughness and the degree of gloss
between its surface and back, and can be produced industrially
advantageously with high producibility and excellent
operability.
Inventors: |
Asai; Takeo (Sagamihara,
JP), Ono; Tadashi (Yokohama, JP) |
Assignee: |
Teijin Limited (Osaka,
JP)
|
Family
ID: |
12906017 |
Appl.
No.: |
07/489,082 |
Filed: |
March 5, 1990 |
Foreign Application Priority Data
Current U.S.
Class: |
428/330; 428/910;
428/900; 428/480; 428/323; 428/143; 428/142; 428/847.7 |
Current CPC
Class: |
C08K
5/098 (20130101); C08J 5/18 (20130101); C08K
3/30 (20130101); C08K 3/30 (20130101); C08L
67/02 (20130101); C08K 5/098 (20130101); C08L
67/02 (20130101); Y10S 428/90 (20130101); Y10T
428/31786 (20150401); Y10T 428/24364 (20150115); Y10T
428/25 (20150115); Y10T 428/258 (20150115); C08J
2367/02 (20130101); Y10T 428/24372 (20150115); Y10S
428/91 (20130101) |
Current International
Class: |
C08K
3/30 (20060101); C08K 5/098 (20060101); C08K
5/00 (20060101); C08J 5/18 (20060101); C08K
3/00 (20060101); B23B 005/16 () |
Field of
Search: |
;428/480,900,141,143,402,694,403,323,330,910 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0186456 |
|
Jul 1986 |
|
EP |
|
62-218969 |
|
Sep 1987 |
|
JP |
|
63-115792 |
|
May 1988 |
|
JP |
|
Other References
Chemical Abstracts, vol. 108, No. 20, May 16, 1988, Abstract No.
177252h..
|
Primary Examiner: Thibodeau; Paul J.
Assistant Examiner: Follett; R.
Attorney, Agent or Firm: Wenderoth, Lind & Ponack
Claims
We claim:
1. A biaxially oriented polyester film comprising of an intimate
mixture of
(a) an aromatic polyester,
(b) 1 to 100 parts by weight, per 100 parts by weight of the
aromatic polyester, of barium sulfate particles having an average
particle diameter of 0.1 to 10 micrometers, and
(c) 0.002 to 0.05 mole, per mole of barium sulfate, of an alkali
metal or alkaline earth metal salt of a higher fatty acid having 8
to 34 carbon atoms, said fatty acid metal salt having a melting
point in the range of 120.degree. to 320.degree. C.
2. The biaxially oriented polyester film of claim 1 in which the
aromatic polyester is a polyester composed of an aromatic
dicarboxylic acid as a main acid component and an alkylene glycol
having 2 to 10 carbon atoms as a main glycol component.
3. The biaxially oriented polyester film of claim 1 in which the
aromatic polyester is polyethylene terephthalate.
4. The biaxially oriented polyester film of claim 1 in which the
barium sulfate particles have an average particle diameter of 0.3
to 5 micrometers.
5. The biaxially oriented polyester film of claim 1 in which the
barium sulfate particles have such a distribution that in the
integrated particle diameter distribution curve, D.sub.75 /D.sub.25
is 0.4 to 0.8.
6. The biaxially oriented polyester film of claim 1 which contains
2 to 33 parts by weight of the barium sulfate particles, per 100
parts by weight of the aromatic polyester (a).
7. The biaxially oriented polyester film of claim 1 in which said
higher fatty acid in (c) is a saturated fatty acid having 8 to 18
carbon atoms.
8. The biaxially oriented polyester film of claim 1 in which the
metal salt of the higher fatty acid is lithium, sodium, calcium or
barium stearate.
9. The biaxially oriented polyester film of claim 1 which has a
thickness of 100 to 300 micrometers.
Description
This invention relates to a biaxially oriented polyester film, and
more specifically, to a biaxially oriented polyester film
containing barium sulfate particles and a higher fatty acid metal
salt.
Polyesters typified by polyethylene terephthalate have excellent
physical and chemical properties, and find extensive use as fibers,
films and other shaped articles. In film applications, white films
are used as substrates of cards, labels, display boards, white
boards, photographic papers and image-forming papers, and
opalescent films having light perviousness and light diffusing
property as substrates of electrically decorative boards,
substrates for drafting and substrates of labels.
It has been well known that to obtain white or opalescent films,
suitable amounts of white inorganic particles are included into
polyesters. Typical examples of the white inorganic particles
include titanium oxide, calcium carbonate, barium sulfate, calcium
sulfate and talc. For obtaining opalescent films, silicon dioxide
may also be used.
Japanese Patent Publication No. 30930/1985 discloses an
image-forming photosensitive material composed of a non-transparent
polyester substrate film containing 5 to 50% by weight, based on
the polyester, of barium sulfate fine particles having an average
particle diameter of 0.5 to 10 micrometers and 99.9% of which have
a particle diameter of not more than 50 micrometers, voids existing
around the fine particles of barium sulfate, and superimposed on
one surface of the substrate polyester film, a photosensitive
image-forming layer.
A biaxially oriented polyester film containing fine particles of
barium sulfate dispersed therein, because of its softness,
supplness and pearlescent luster attributed to void formation, can
be expected to find applications as an image-forming photosensitive
material, for example as a base of a photographic paper and a base
of films for various hard copies.
However, the problem with the biaxially oriented polyester film
containing fine particles of barium sulfate is that its surface
properties, such as surface roughness and the degree of gloss,
differ between its surface and back. The difference increases with
increasing film thickness, and becomes particularly marked when the
thickness of the unstretched film is 1 mm or more. In addition, as
the thickness of the unstretched film increases, its stretchability
is reduced accordingly, and the frequency of film breakage
increases.
It is an object of this invention to provide a biaxially oriented
polyester film having a novel composition.
Another object of this invention is to provide a biaxially oriented
polyester film having substantially no difference in surface
properties such as surface roughness and the degree of gloss
between its surface and back.
Still another object of this invention is to provide a biaxially
oriented polyester film which can be produced industrially
advantageously with high producibility and excellent
operability.
Other objects of this invention along with its advantages will
become apparent from the following description.
In accordance with this invention, the above objects and advantages
of the invention are achieved by a biaxially oriented polyester
film comprising of an intimate mixture of
(a) an aromatic polyester,
(b) 1 to 100 parts by weight, per 100 parts by weight of the
aromatic polyester, of barium sulfate particles having an average
particle diameter of 0.1 to 10 micrometers, and
(c) 0.002 to 0.05 mole, per mole of barium sulfate, of an alkali
metal or alkaline earth metal salt of a higher fatty acid having 8
to 34 carbon atoms, said fatty acid metal salt having a melting
point in the range of 120.degree. to 320.degree. C.
Investigations of the present inventors have shown that when a
conventional polyester is melted and extruded onto a casting drum
through a die and quenched and solidified to form an unstretched
film, its surface or surface layer on that side which did not
contact the casting drum is crystallized or is liable to be
crystallized, but that if a certain type of fatty acid metal salt
is used together with the barium sulfate particles, the action of
the barium sulfate particles to promote crystallization of the
polyester during temperature fall can be inhibited, and therefore
that the film does not break in the stretching step and the film
can be stably stretched biaxially to give a biaxially oriented
polyester film having substantially no difference between its
surface and back. This finding constitutes the basis of providing
the biaxially oriented polyester film of this invention.
The aromatic polyester (a) constituting the biaxially oriented
polyester film of this invention is preferably derived from an
aromatic dicarboxylic acid as a main acid component and an alkylene
glycol having 2 to 10 carbon atoms as a main glycol component.
Examples of the aromatic dicarboxylic acid include terephthalic
acid, isophthalic acid, naphthalenedicarboxylic acid,
diphenoxyethanedicarboxylic acid, diphenyldicarboxylic acid,
diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid,
diphenylketonedicarboxylic acid and anthracenedicarboxylic acid.
The terephthalic acid and naphthalene-2,6-dicarboxylic acid are
particularly preferred.
Examples of the alkylene glycol include alkylene glycols having 2
to 10 carbon atoms, such as ethylene glycol, trimethylene glycol,
tetramethylene glycol, pentamethylene glycol and hexamethylene
glycol. Of these, ethylene glycol and tetramethylene glycol are
especially preferred.
The aromatic polyester composed of the aromatic dicarboxylic acid
component and the glycol component can be produced by the following
method of producing polyethylene terephthalate taken as an example.
This method comprises a first step of forming a glycol ester of
terephthalic acid and/or its low polymer by directly esterifying
terephthalic acid and ethylene glycol, esterinterchanging dimethyl
terephthalate and ethylene glycol or by reacting terephthalic acid
with ethylene oxide, and a second step of polycondensing the
reaction product of the first step.
The aromatic polyester used in this invention may have a third
component copolymerized or blended therewith. When the third
component is to be copolymerized, its amount is usually limited to,
preferably, not more than 20 mole % of the total amount of the acid
component. If the third component is to be blended, its amount is
desirably limited to not more than 20% by weight based on the
entire composition.
Examples of the third component include aliphatic dicarboxylic
acids, alicyclic dicarboxylic acids, aromatic dioxy compounds,
alicyclic glycols, aliphatic glycols having an aromatic ring,
polyalkylene glycols, aliphatic hydroxycarboxylic acids, aromatic
hydroxycarboxylic acids, functional derivatives of these compounds,
polyethers, polyamides, polycarbonates and polyolefins.
The above aromatic polyesters include those to which trifunctional
or higher compounds, or monofunctional compounds are bonded in such
proportions that the resulting polyesters are regarded as being
substantially linear. They may contain catalysts and stabilizers,
and as required antioxidants, plasticizers, dispersants and
antistatic agents.
The aromatic polyester used in this invention is preferably a
polyester derived from terephthalic acid as a main acid component
and ethylene glycol as a main glycol component, typically
polyethylene terephthalate.
The barium sulfate particles (b) constituting the biaxially
oriented polyester film of the invention have an average particle
diameter of 0.1 to 10 micrometers.
The barium sulfate particles that can be used are not limited by
the method of preparation. For example, precipitated barium sulfate
and water-ground barium sulfate are preferably used. These barium
sulfate particles can be easily obtained commercially. The barium
sulfates should have an average particle diameter of 0.1 to 10
micrometers, preferably 0.3 to 5 micrometers. If the average
particle diameter of barium sulfate falls outside the range of 0.1
to 10 micrometers, the film-formability of the polyester and the
surface properties of the biaxially oriented polyester film of the
invention are outside the scope of the invention.
Preferably, the barium sulfate particles have a sharp particle
diameter distribution. For this reason, before mixing them with the
aromatic polyester, the barium sulfate particles may be subjected
to a classifying treatment such as a filtration method, a
precipitation classifying method, a wind classifying method or a
sand grinding method. In the cumulative particle diameter
distribution curve taken from larger diameters, the ratio of the
particle diameter at 75 cumulative % by weight (D.sub.75) to that
at 25 cumulative % by weight (D.sub.25), D.sub.75 /D.sub.25, is
from 0.4 to 0.9, preferably from 0.4 to 0.8.
The barium sulfate particles are present in a proportion of 1 to
100 parts by weight, preferably 2 to 33 parts by weight, per 100
parts by weight of the aromatic polyester. This proportion is
determined from the standpoint of ensuring good film stretching
property and good film properties (such as surface roughness,
gloss, dynamic properties, etc.).
The proportion of the barium sulfate particles is desirably 2 to 5%
by weight for an application in which the transmission and
diffusion of light are utilized as in electrically decorative
board, and 15 to 20% by weight in an application in which the light
shielding properties are utilized as in a white card or a
photographic paper base (a support for a photographic emulsion
layer).
The higher fatty acid metal salt (c), another component of the
biaxially oriented polyester film of the invention, is present in a
proportion of 0.002 to 0.05 mole, per mole of barium sulfate.
The higher fatty acid metal salt (c) is an alkali metal or alkaline
earth metal salt of a higher fatty acid having 8 to 34 carbon atoms
and has a melting point of 120.degree. to 320.degree. C.
The higher fatty acid may be saturated or unsaturated, and
preferably has 8 to 18 carbon atoms. Higher fatty acid metal salts
having a melting point of less than 120.degree. C. are undesirable
because they are prone to evaporate during the melt extrusion of
the polyester, during the film formation, and the heat causes the
higher fatty acid metal salt to bleed out to the film surface and
will contaminate the surface of rolls during film formation. On the
other hand, higher fatty acid metal salts having a melting point
higher than 320.degree. C. are difficult to disperse uniformly in
the polyester. The preferred melting point of the higher fatty acid
metal salts is 150.degree. to 280.degree. C. Further, in relation
to the polyester forming the film, the melting point of the higher
fatty acid metal salt desirably should not be 50.degree. C. or more
higher than the melting point of the polyester, and preferably not
higher than the melting point of the polyester by 20.degree. C.
Examples of suitable higher fatty acid metal salts are saturated
higher fatty acid salts such as calcium pelargonate, calcium
laurate, barium laurate, magnesium laurate, lithium laurate, barium
stearate, lithium stearate, sodium stearate, magnesium stearate,
calcium stearate, sodium palmitate, magnesium palmitate, potassium
palmitate and sodium montanate. Preferred are barium stearate and
lithium stearate.
The amount of the higher fatty acid metal salt is 0.002 to 0.05
mole, preferably 0.005 to 0.05 mole, per mole of barium sulfate. If
it is less than 0.002 mole, it cannot give rise to the substantial
affect of inhibiting the crystallization of the polyester during
temperature fall. On the other hand, if it exceeds 0.05 mole, the
effect of inhibiting the crystallization of the polyester nearly
reaches saturation, and does not further increase. If the
proportion further increases, the inhibiting effect rather tends to
decrease.
The biaxially oriented polyester film of this invention can be
produced from an intimate mixture of the aromatic polyester, barium
sulfate and the higher fatty acid metal salt. This intimate mixture
may be produced, for example, by adding barium sulfate particles
and the higher fatty acid metal salt during the polyester
production, particularly to the esterification product or the
ester-interchange product, or to the polyester as produced. It may
also be produced by preparing a polyester containing one of the
additives, then adding the other additive, and melt-kneading the
resulting mixture, or by preparing a polyester containing one of
the additives and a polyester containing the other additive, and
melt-kneading the two polyesters, or by melt-kneading polyester
chips with barium sulfate particles and the higher fatty acid metal
salt simultaneously.
The last method described above is preferred because the effect of
inhibiting the crystallization of the polyester is higher than the
other methods. As a modified version of this method, there may be
advantageously used a method comprising preparing master chips
containing barium sulfate particles and the higher fatty acid metal
salt in a predetermined ratio in high concentrations and
melt-kneading them with polyester chips not containing these
additives.
As required, the above intimate mixture may contain a suitable
amount of inorganic fine particles other than the barium sulfate
particles for improving the hiding property (light shielding
property) of the biaxially oriented film or controlling its surface
roughness, or a fluorescent bleaching agent, a colored pigment or a
dye to control the color of the film.
The biaxially oriented polyester film can be produced by a
successive biaxial stretching method, a simultaneous biaxial
stretching method, or an inflation method. The successive biaxial
stretching method is preferred.
In the successive biaxial stretching method or the simultaneous
biaxial stretching method, the intimate mixture is melt-extruded
through a die and quenched and solidified on a casting drum kept at
about 20.degree. to 40.degree. C. to obtain an unstretched film. At
this time, that surface of the film which makes contact with the
surface of the casting drum is quenched, but cooling of its
opposite side is retarded. In particular, when the thickness of the
unstretched film is 1 mm or larger, this retardation becomes
marked, and crystallization proceeds in this surface (opposite
side). As a result, the surface of the film after biaxial
stretching becomes rough, and the resulting film markedly differs
in surface properties between its surface and back. This phenomenon
can be observed to some extent when the film does not contain
barium sulfate particles. It is very conspicuous when the film
contains barium sulfate particles. Furthermore, since the
processability of the film is degraded, the film tends to
break.
The above phenomenon can be avoided or reduced in this invention by
using the above intimate mixture containing barium sulfate
particles and the higher fatty acid metal salt. However, forced
cooling of the film by blowing cold air at a high speed against the
unstretched film on the casting drum from an air side surface (that
surface which is opposite to that surface which is in contact with
the casting drum) is desirable in the production of the film of the
invention.
The unstretched film used desirably has a thickness of at least
about 1 mm, for example 1.1 to 3.0 mm.
The unstretched film is then stretched under conditions generally
well known. For example, it is stretched in one direction to 1.5 to
4.5 times, and in a direction at right angles thereto to 1.5 to 4.5
times at an area ratio of 6 to 15. The stretching temperature is
preferably 20.degree. to 70.degree. C. higher than the glass
transition temperature (Tg) of the polyester constituting the film.
As required, after biaxial stretching, the film may be heat-set.
The heat-setting temperature is preferably 15.degree. to
100.degree. C. lower than the melting point of the polyester.
The resulting biaxially oriented polyester film of this invention
preferably has a thickness of, for example, 100 to 300
micrometers.
Thus, the present invention can provide a biaxially stretched
polyester film containing barium sulfate particles having
substantially no diffrence in surface properties (particularly,
surface roughness and the degree of gloss) between its surface and
back while retaining the advantages of conventional biaxially
oriented films containing barium sulfate particles.
The biaxially oriented polyester films of the invention has the
advantage that it can be produced with stable processability. The
biaxially oriented polyester film of the invention can be utilized
as substrates of cards, labels, display boards, white boards,
photographic papers and image-forming papers, electrically
decorative boards, and drafting.
The following examples illustrate the present invention in further
detail. All parts in these examples are by weight, and the various
properties are measured by the following methods.
(1) Inherent Viscosity
The polymer was dissolved in ortho-chlorophenol, and its solution
viscosity was measured at 35.degree. C. The inherent viscosity was
determined from the solution viscosity.
(2) Crystallization Temperature During Temperature Fall Tcd
(.degree.C)
About,10 g of film was sampled from a film sample, melted at
290.degree. C., and quenched to form a measurement sample. By using
DSC/20 Type made by Seiko Denshi Kogyo Co., Ltd., the temperature
of the sample was elevated to 290.degree. C. at a rate of
20.degree. C./min., and the sample was maintained at this
temperature for 2 minutes. Then, its temperature was lowered at a
rate of 20.degree. C./min., and its crystallization temperature was
measured.
(3) Surface Roughness Ra (Micrometers)
A surface roughness tester SE-30C (made by Kosaka Kenkyusho K.K.)
was used, and the surface roughness was measured in accordance with
JIS B 0601-1976. The number of measured samples (n) was 5. The
maximum measured value was excluded, and the average value of the
remaining four measured values was calculated and defined as the
centerline average roughness Ra.
(4) DEGREE OF GLOSS GS (60.degree.)
Measured in accordance with JIS Z 8741-1962 by using a glossmeter
(GM-3D made by Murakami Color Technology Laboratory Co., Ltd.). The
measuring angle was adjusted to 60.degree., and the number of
measuring samples was 5. The average values of the five measured
samples was defined as the degree of gloss Gs (60.degree.).
(5) Melting Point (.degree.C)
Measured by using a micro-melting point apparatus made by
Yanagimoto Seisakusho K. K.
(6) Average Particle Diameter of the Particles
The particles were subjected to a centrifugal particle size
analyzer (Model CAPA-500 made by Horiba Seisakusho Co., Ltd.). From
the cumulative curve of particles of the individual diameters and
their amounts calculated on the basis of the resulting centrifugal
sedimentation curve, a particle diameter corresponding to a 50 mass
percent was read and defined as the average particle diameter of
the particles (see "Particle Size Measuring Technique", pages
242-247, 1975, published by Nikkan Kogyo Press).
(7) Sharpness of the Particle Diameter Distribution
In the cumulative curve obtained in the above average particle
diameter measurement, the weight percents of particles integrated
beginning with larger particles. The particle diameters
corresponding to 25% and 75% of the entire particle weight are
defined as D.sub.25 and D.sub.75, respectively. The sharpness S of
the particle size distribution is defined by the following
equation. ##EQU1##
(8) Break Strength, Break Elongation and F-5 Value
A film sample, 10 mm in width, and 150 mm in length, was taken. It
was pulled by a Instron type universal tensile tester at a pulling
speed of 100 mm/min. with an interchuck distance of 100 mm, and a
chart speed of 100 mm/min. until the film broke. The strength and
elongation of the film at break are the break strength and break
elongation. The strength of the film at 5% stretch was divided by
the sectional area of the initial sample, and the quotient was
defined as F-5 value.
EXAMPLES 1-3 AND COMPARATIVE EXAMPLES 1 and 2
A reactor was charged with 96 parts of dimethyl terephthalate, 58
parts of ethylene glycol, 0.038 part of manganese acetate and 0.041
part of antimony trioxide, and with stirring, ester-interchange
reaction was carried out until the temperature of the inside of the
reactor reached 240.degree. C. while methanol was distilled. After
the ester-interchange reaction was terminated, 0.097 part of
trimethyl phosphate was added. Subsequently, the reaction product
was heated, and polycondensed under high vacuum at 280.degree. C.
finally to give a polyester having an inherent viscostiy of 0.64
(polyester A).
The polyester A and fine particles of precipitated barium sulfate
having an average particle diameter of 0.7 micrometers were
respectively dried at 170.degree. C. for 3 hours, and fed into a
twin-screw extruder so that the concentration of barium sulfate was
40% by weight, and melt-kneaded at 280.degree. C. The mixture was
quenched and solidified to give master chips (to be referred to as
polyester B).
The polyester A was dried at 170.degree. C. for 3 hours, and barium
stearate was dried at 120.degree. C. for 1 hour. They were fed into
a twin-screw extruder s that the concentration of barium stearate
in the polymer was 3% by weight. They were melt-kneaded at
280.degree. C., and quenched and solidified to obtain master chips
(to be referred to as polyester C).
Polyesters A, B and C were blended and dried at 160.degree. C. so
that the concentration of barium sulfate in the polymer reached 20%
by weight and the amount in mole per mole of barium sulfate, of
barium stearate was as shown in Table 1. The mixture was then
melt-extruded at 280.degree. C., and quenched and solidified on a
casting drum kept at 40.degree. C. to obtain an unstretched film.
The unstretched film was stretched longitudinally to 3.3 times at
90.degree. C., and then transversely to 3.6 times at 105.degree. C.
The stretched film was heat-treated at 235.degree. C. to give a
biaxially oriented film having a thickness of 200 micrometers. The
properties of the films obtained are shown in Table 1.
COMPARATIVE EXAMPLE 3
Example 1 was repeated except that polyester C was not used (i.e.,
barium stearate was not included into the polymer). Thus, a
biaxially oriented film having a thickness of 200 micrometers was
obtained. During film formation, especially in the step of
longitudinally stretching the unstretched film, stretching
unevenness occurred, and the film frequently broke. The properties
of the film are shown in Table 1.
EXAMPLE 4 AND 5
Polyester A and precipitated barium sulfate having an average
particle diameter of 0.7 micrometer were dried at 170.degree. C.
for 3 hours, and barium stearate was dried at 120.degree. C. for 1
hour. Then, these materials were fed into a twin-screw extruder so
that the concentration of barium sulfate in the polymer reached 40%
by weight, and the amount in moles of barium stearate per mole of
barium sulfate was as shown in Table 1. They were melt-kneaded at
280.degree. C. and quenched and solidified to form master chips (to
be referred to as polyester D).
Then, polyester A was blended with the polyester D so that the
concentration of barium sulfate in the polymer was 18% by weight
(the amount of barium stearate was as shown in Table 1). The blend
was worked up in the same way as in Example 1 to give biaxially
stretched films. The properties of the films are shown in Table
1.
EXAMPLE 6
Example 4 was repeated except that lithium stearate in the amount
shown in Table 1 was used instead of barium stearate. A biaxially
oriented film having a thickness of 200 micrometers was obtained.
Its properties are shown in Table 1.
It is seen from the results given in Table 1 that the films
obtained in the Examples are biaxially oriented films containing
fine particles of barium sulfate, and they had very little
differences in surface properties between the surface and back, and
that the films were obtained with stable processability.
TABLE 1
__________________________________________________________________________
Concentration Fatty acid metal salt Time of adding Thickness of
Crystallization Surface roughness of barium sulfate Main the fatty
the film temperature, Ra (.mu.m) Run No. (wt. %) component Moles
acid salt (.mu.m) Tcd (.degree.C.) D surface A
__________________________________________________________________________
surface Example 1 20 A 0.010 X 200 214 0.051 0.057 Example 2 20 A
0.015 X 200 210 0.050 0.054 Example 3 20 A 0.030 X 200 213 0.051
0.053 Comparative 20 A 0.001 X 200 221 0.053 0.067 Example 1
Comparative 20 A 0.070 X 200 219 0.052 0.053 Example 2 Comparative
20 A 0 -- 200 222 0.052 0.069 Example 3 Example 4 18 A 0.005 Y 200
204 0.051 0.053 Example 5 18 A 0.015 Y 200 205 0.052 0.054 Example
6 18 B 0.020 Y 200 207 0.052 0.055
__________________________________________________________________________
Degree of gloss, Break strength Break elongation F-5 value Gs
(60.degree. C.) (%) (kg/mm.sup.2) (%) (kg/mm.sup.2) Run No. D
surface A surface MD TD MD TD MD TD
__________________________________________________________________________
Example 1 62 54 15.2 16.3 83 80 10.2 10.3 Example 2 63 57 15.0 16.5
80 79 10.3 10.3 Example 3 62 59 15.5 16.3 85 81 10.5 10.7
Comparative 61 43 15.0 16.3 80 78 9.8 10.0 Example 1 Comparative 61
57 15.1 16.0 82 78 9.7 10.0 Example 2 Comparative 61 42 14.9 16.1
79 77 9.5 9.8 Example 3 Example 4 63 58 16.3 17.4 97 91 9.9 10.1
Example 5 63 57 16.2 17.3 95 90 9.9 10.1 Example 6 62 56 16.1 17.0
92 90 9.7 10.0
__________________________________________________________________________
Note Main component A: barium stearate Main component B: lithium
stearate Moles: per mole of barium sulfate Time of addition X:
Master chips of polyethylene terephthalate containing barium
sulfate and master chips of polyethylene terephthalate containing
the fatty acid metal salt were separately prepared, and then
blended with master chips of polyethylene terephthalate not
containing these additives Time of addition Y: Master chips of
polyethylene terephthalate to which barium sulfate and the fatty
acid metal salt were simultaneously incorporated were prepared and
then blended with master chips of polyethylene terephthalate. D
surface: That surface of the film which contacted the surface of
the casting drum during film formation. A surface: The surface
opposite to D surface. MD: Machine direction TD: The direction at
right angles to the machine direction
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